A selection of the branches will be turned into restaurants with dimmed lighting, classical music, roses, candelabras, white linen tablecloths and table service.
A four-course menu will be made up of Greggs food with a "special Valentine’s twist". This includes a main dish of a choice of "signature Greggs puff pastry parcel, freshly baked to order, accompanied by oven roasted spiced potato slices and a garnish of fresh Apollo spinach leaves and sunblush tomatoes".
The experience will be available at the London Stockwell, Manchester City Tower, Glasgow Argyle Street, Newcastle Grainger Street and Cardiff Queen Street branches.
Couples will be able to book a table through OpenTable for the experience which costs £15. The activation has been created by PR agency Taylor Herring.